The campaign included Labour activists in tail-coats and top hats shadowing Mr Timpson, and leaflets referring to his "mansion" and his wealth.

Mr Timpson, part of the family that founded the Timpson chain of cobblers' shops, lives 15 miles from the constituency. It emerged during the campaign that Tamsin Dunwoody, the Labour candidate, lives in Wales in a house larger than her Tory rival's.

The aggressive, class-based campaign against Mr Timpson made some senior Labour figures uneasy, but it had the tacit blessing of Gordon Brown, the Prime Minister.

The campaign was run in Crewe by Steve McCabe, a Labour whip and partner of Fiona Gordon, Mr Brown's political secretary. She is leaving Downing Street later this year.

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Government insiders say the class-based tactics were employed despite the advice of Stephen Carter, Mr Brown's chief strategist. He is understood to have argued that voters are not concerned about a politician's background.

Instead, No 10 polling and focus group research suggests that Mr Cameron is most vulnerable to suggestions that he is too slick and superficial, with sceptical voters comparing him to an estate agent or a marketing man.

In a Commons exchange earlier this month, Mr Brown last month branded Mr Cameron "a shallow salesman," and the experience in Crewe may mean Labour alters its approach to make more such attacks.

Mr McCabe insisted he had "no regrets" about the "Toff" campaign.

He said: "That was a bit of a joke, and it was milder than a lot stuff I've seen in by-elections elsewhere."